core-api/irq/irq-affinity.rst

2 SMP IRQ affinity
6 	- Started by Ingo Molnar <mingo@redhat.com>
7 	- Update by Max Krasnyansky <maxk@qualcomm.com>
14 IRQ affinity then the value will not change from the default of all cpus.
16 /proc/irq/default_smp_affinity specifies default affinity mask that applies
17 to all non-active IRQs. Once IRQ is allocated/activated its affinity bitmask
21 Here is an example of restricting IRQ44 (eth1) to CPU0-3 then restricting
22 it to CPU4-7 (this is an 8-CPU SMP box)::
31 	[root@moon 44]# ping -f h
34 	--- hell ping statistics ---
36 	round-trip min/avg/max = 0.1/0.1/0.4 ms
39 …       1785       1785       1783         0          0           0         0    IO-APIC-level  eth1
42 processors (0-3).
43 Now lets restrict that IRQ to CPU(4-7).
50 	[root@moon 44]# ping -f h
53 	--- hell ping statistics ---
55 	round-trip min/avg/max = 0.1/0.5/585.4 ms
58 …       1785       1785       1783      1784       1069        1070       1069   IO-APIC-level  eth1
61 i.e counters for the CPU0-3 did not change.
65 	[root@moon 44]# echo 1024-1031 > smp_affinity_list
67 	1024-1031